1. Field of the Invention
The present invention relates, in general, to an oil separator for compressors of automobile refrigeration systems and, more particularly, to an internal oil separator installed within the compressor of such a refrigeration system and used for separating and recovering lubrication oil from discharged gas refrigerant before the refrigerant is discharged from the compressor through a refrigerant discharge line and feeding the recovered oil back to the frictional parts of the compressor.
2. Description of the Prior Art
As well known to those skilled in the art, a refrigeration system for automobiles typically comprises a compressor, a condenser, an expansion valve and an evaporator. In such a refrigeration system, the compressor adiabatically compresses low temperature and low pressure gas refrigerant, thus forming high temperature and high pressure gas refrigerant prior to discharging the refrigerant to a condenser. The condenser condenses the high temperature and high pressure gas refrigerant from the compressor through a heat exchanging process, thus forming saturated liquid refrigerant. The expansion valve throttles the saturated liquid refrigerant from the condenser, thus allowing the refrigerant to become a saturated wet vapor phase having low pressure. In the evaporator, the refrigerant from the expansion valve absorbs heat from its surroundings, thus becoming a saturated gaseous phase prior to returning to the compressor.
In such a refrigeration system for automobiles, the compressor is operated by the rotating force of the engine, which is selectively transmitted thereto through a pulley under the control of an electromagnetic clutch. The compressor thus sucks the saturated gas refrigerant from the evaporator and compresses the refrigerant by a rectilinear reciprocating action of a piston prior to discharging the refrigerant to the condenser. Such compressors have been typically and generally classified into two types, that is, reciprocating compressors and rotary compressors, in accordance with both the refrigerant compression styles and the structures of the compressors. In addition, the reciprocating compressors have been classified into two types, swash plate compressors and wobble plate compressors. On the other hand, the rotary compressors have been classified into two types, vane rotary compressors and scroll compressors.
A swash plate compressor comprises a front housing, and a rear housing assembled with the front housing into a single housing. A front cylinder is installed within the front housing, while a rear cylinder is installed within the rear housing. A plurality of double-head pistons are movably positioned within the bores of the front and rear housing so as to rectilinearly reciprocate relative to the bores. A drive shaft is rotatably installed in the compressor while passing through the central portions of the front and rear housings and the front and rear cylinders. A swash plate is inclinedly mounted to the drive shaft and is rotated along with the drive shaft, thus allowing the double-head pistons to rectilinearly reciprocate relative to the bores of the cylinders. A valve unit is installed in the gap between each of the front and rear cylinders and the interior surface of an associated one of the front and rear housings.
When the rotating force of an engine is applied to the drive shaft of the above swash plate compressor, the swash plate is rotated along with the drive shaft, thus allowing the double-head pistons to rectilinearly reciprocate within the bores of the front and rear cylinders. During such a reciprocating action of the pistons, refrigerant is sucked into the bores of the cylinders through a valve unit in the case of a suction stroke of the cylinders. On the other hand, refrigerant is compressed and discharged from the bores of the cylinders through another valve unit in the case of an discharge stroke of the cylinders.
In order to allow such a swash plate compressor to be smoothly operated, it is necessary to make refrigerant laden with lubrication oil. In such a case, the lubrication oil effectively circulates along with the refrigerant through the drive parts within the compressor during an operation of the refrigeration system, thus lubricating the gaps between the mechanically frictional drive parts within the compressor, such as the gaps between the pistons and cylinder bores.
When such lubrication oil circulates along with refrigerant within the refrigeration system as described above, the oil passes through the heat exchangers, such as the condenser and evaporator, and through the expansion valve and a variety of pipes and hoses. The oil is thus undesirably coated on the interior surfaces of the refrigerant passages within the refrigeration system and consumes the space of the interior cavity of the parts of the system, particularly, the heat exchangers. This finally reduces the fluidity of refrigerant within the refrigeration system in addition to a reduction in heat exchanging effect of the refrigeration system. Such a coated oil layer also increases the pressure drop within the heat exchangers, and so the operational effect of the refrigeration cycle is deteriorated. On the other hand, the circulation of oil through all the parts of the refrigeration system inevitably results in a variation in the amount of oil laden in the refrigerant fed to the compressor. Therefore, lubrication oil fails to be sufficiently supplied to the drive parts within the compressor, and so it is almost impossible to accomplish a desired lubrication effect for the frictional drive parts of the compressor. This causes such frictional drive parts of the compressor to be operated without being effectively lubricated, thus finally causing frictional damage or breakage of the drive parts and reducing the durability of the compressor. When refrigerant is laden with a large quantity of lubrication oil so as to allow the drive parts of the compressor to be sufficiently lubricated, the refrigerant may lose its intrinsic refrigerating function due to the oil. This finally reduces the refrigerating operational efficiency of the refrigeration system and increases the size of the system. It is difficult to design such an enlarged refrigeration system or to install the system at a limited area within the engine compartment of an automobile.
In an effort to overcome the above-mentioned problems, the automobile refrigeration systems are typically provided with oil separators for separating and recovering lubrication oil from discharged gas refrigerant of a compressor and feeding the recovered oil back to the compressor.
Such oil separators for compressors have been typically classified into two types, internal oil separators installed within compressors and external oil separators installed outside the compressors, in accordance with the position of the oil separators relative to the compressors. The two types of oil separators respectively have advantages and disadvantages as follows.
FIG. 16 is a circuit diagram of a refrigeration system provided with a conventional external oil separator. As shown in the drawing, the external oil separator 110 is installed on a refrigerant discharge line 112 outside the compressor 100, and so the external oil separator 110 is so-called "a refrigerant discharge line oil separator" in the art. Such an oil separator 110 separates and recovers lubrication oil from refrigerant discharged from the compressor 100 through the discharge line 112 and stores the recovered oil in its oil chamber, and feeds the recovered oil back to the refrigerant suction line 111 of the compressor 100 through an oil flow controller (not shown), such as a capillary tube. The above oil separator 110 thus allows the lubrication oil to repeatedly circulate within the compressor 100 so as to lubricate the drive parts (not shown) of the compressor 100 without being fed to the other parts of the refrigeration system. In the drawing, the reference numerals 130, 140, 150 and 160 respectively denote a condenser, a receiver drier, an expansion valve and an evaporator of the refrigeration system.
In a brief description, the external oil separator 110 separates and recovers lubrication oil from discharged refrigerant of the compressor 100 and bypasses the recovered oil to the oil suction line 111 of the compressor 100 through a bypass line 113.
Such an external oil separator 110 is advantageous in that the separator 110 is somewhat easy to design and produce and to accomplish a desired oil separating and recovering effect. However, the external oil separator 110 is problematic in that it is necessarily provided with a bypass line 113 consuming the space within the refrigeration system.
Meanwhile, several types of internal oil separators have been proposed and selectively used with different types of compressors.
An example of conventional internal oil separators for compressors is referred to an oil separator disclosed in Japanese Patent Laid-open Publication No. Heisei. 5-240158. As shown in FIG. 17, this Japanese internal oil separator comprises an oil-storing chamber 122, which separates and recovers lubrication oil from refrigerant discharged from the cylinder bore of a compressor 120 and primarily stores the recovered oil therein. An oil supply chamber 124 is formed in parallel to the oil-storing chamber 122 and receives the recovered oil discharged from the oil-storing chamber 122 through an oil line 123 due to a pressure difference between the two chambers 122 and 124, thus secondarily storing the oil therein. An oil return line 126 connects the oil supply chamber 124 to a driving part chamber 128 formed within the lower portion of an oil separator housing 121, thus guiding the recovered oil from the oil supply chamber 124 to the driving part chamber 128. An oil flow control valve 125 is installed on the inlet port of the oil return line 126 so as to control the quantity of inlet oil for the line 126. In such an internal oil separator, it is necessary to parallely form the two chambers, or the oil-storing chamber 122 and the oil supply chamber 124, within the housing 121, and so the oil-storing chamber 122 is undesirably limited in its size. This finally limits the oil storage capacity of the oil-storing chamber 122. When the size of the oil-storing chamber 122 is enlarged to store a desired quantity of oil therein, the size of the compressor 120 is also enlarged. However, it is difficult to install such a large-sized compressor 120 at a limited area within the engine compartment of an automobile. In addition, when the automobile is moved to the left or right so as to inclinedly position the compressor 120 while running on bumpy road, the surface of recovered oil 127 within the oil-storing chamber 122 changes from a horizontal position "A" to an inclined position "B" as shown in FIG. 17 while opening the inlet port 129 of the oil line 123 extending between the two chambers 122 and 124. When the inlet port 129 of the oil line 123 is opened as described above, gas refrigerant in place of recovered oil is undesirably introduced into the driving part chamber 128 through the open inlet port 129. In such a case, the compressor 120 is seriously damaged.
In the prior art, several types of internal oil separators for compressors in addition to the above Japanese oil separator have been proposed and used. However, such internal oil separators are designed to be operated under the operational theory similar to that of the above Japanese oil separator, and so it is possible for those skilled in the art to effectively understand the construction and operation of the internal oil separators from the following simple description without reference to the drawings.
In an internal oil separator for compressors disclosed in Japanese Patent Laid-open Publication No. Heisei. 3-129273, a cylindrical cavity is formed within a compressor and is used for guiding compressed and oil-laden gas refrigerant from the compressor into an oil-separating chamber. This oil-separating chamber has an inlet port, through which the oil-separating chamber is connected to the cylindrical cavity. The oil-separating chamber also has an outlet port and is connected to an oil-storing chamber through an oil guide line extending from the outlet port. The oil-storing chamber is used for storing recovered oil therein. Both the oil-separating chamber and the oil-storing chamber are integrated with the compressor into a single structure. Therefore, when the compressed and oil-laden gas refrigerant circulates within the oil-separating chamber while flowing along the internal surface of that chamber, the lubrication oil is separated and recovered from the refrigerant and is guided to the oil-storing chamber prior to being fed back to the suction port of the compressor. In such a case, the gas refrigerant free from lubrication oil is discharged from the compressor into a condenser through a refrigerant discharge line. However, this oil separator is problematic in that it is provided within the top portion of the compressor, thus increasing the size of the compressor and forcing the installation space for the compressor within the engine compartment of an automobile to be enlarged. This finally makes it difficult to design both the compressor and the engine compartment. In addition, since the compressed and oil-laden gas refrigerant flows along the internal surface of the oil-separating chamber while swirling on the surface so as to be centrifugally separated from the oil, the gas refrigerant flows within the oil-separating chamber at a high speed and may be discharged from the compressor along with the lubrication oil. That is, the lubrication oil may be not effectively recovered from the gas refrigerant by the oil separator, but may be undesirably discharged along with the gas refrigerant from the compressor into the condenser. This internal oil separator is thus reduced in oil recovering efficiency.
Another internal oil separator for vane compressors, disclosed in Japanese Patent Laid-open Publication No. Heisei. 7-151083, is designed to prevent a bypass flow of refrigerant within a compressor. In this oil separator, lubrication oil is separated and recovered from gas refrigerant within an oil-separating chamber and is stored within an oil-storing chamber. The gas refrigerant free from oil is discharged from the compressor into a condenser through a refrigerant discharge line. A line control means is installed on the refrigerant discharge line so as to automatically close the line when a rotor is stopped. This oil separator is positioned within the rear section of the compressor. However, the two chambers of this oil separator, or the oil-separating chamber and the oil-storing chamber, exceedingly consume the rear section of the interior space of the compressor, and so this oil separator undesirably increases the size of the compressor. Another problem of this oil separator resides in that it centrifugally separates lubrication oil from gas refrigerant by use of a high speed swirling action of the compressed and oil-laden gas refrigerant within the oil-separating chamber, thus being reduced in oil recovering efficiency in the same manner as that described for the oil separator disclosed in Japanese Patent Laid-open Publication No. Heisei. 3-129273.
Conventional internal oil separators for scroll compressors may be referred to Japanese Patent Laid-open Publication Nos. Heisei. 11-82335, 11-82338, 11-82351, 11-82352 and 11-93880. In the internal oil separators for scroll compressors, an oil-separating chamber is formed at the upper portion of the rear wall of the rear housing within a compressor. An oil-storing chamber, communicating with the oil-separating chamber and used for storing recovered oil therein, is provided between the rear housing and a cell. This oil-storing chamber also communicates with the sliding part between a fixed scroll and a movable plate. This oil separator is designed to centrifugally separate lubrication oil from gas refrigerant by use of a high-speed swirling action of the compressed and oil-laden gas refrigerant in the same manner as that described for the oil separators disclosed in Japanese Patent Laid-open Publication Nos. Heisei. 3-129273 and 7-151083. Therefore, the internal oil separators for scroll compressors are problematic in that lubrication oil may be not recovered from the gas refrigerant, but may be undesirably discharged along with gas refrigerant from the compressor into the condenser, thus being reduced in oil recovering efficiency. Another problem of the above internal oil separators for scroll compressors resides in that the compressor is necessarily enlarged in its length and is complicated in its construction due to both the oil-storing chamber provided between the rear housing and the cell and the oil-separating chamber provided at the upper portion of the rear wall of the rear housing within the compressor.
In an effort to overcome the above-mentioned problems, the inventor of this invention proposed an internal oil separator for compressors in Korean Patent Laid-open Publication No. 99-80933. In this Korean oil separator, both an oil-separating chamber and an oil-storing chamber are formed within a compressor by both the rear housing and the end cap of a compressor in a way such that the oil-separating chamber is positioned above the oil-storing chamber. The interior of the oil-separating chamber is partitioned into two parts by a guide wall, with a U-shaped passage being provided within the oil-separating chamber. In an operation of this oil separator, compressed and oil laden gas refrigerant circulates within the oil-separating chamber while forming a U-shaped circulation. During such a U-shaped circulation of the gas refrigerant within the oil-separating chamber, lubrication oil is centrifugally separated from gas refrigerant prior to being stored in the oil-storing chamber. The recovered oil is, thereafter, fed from the oil-storing chamber back to the driving part chamber of the compressor through an oil return line. In this oil separator, compressed and oil-laden gas refrigerant circulates within the oil-separating chamber while forming a U-shaped circulation, and so the lubrication oil, having a specific weight higher than that of the gas refrigerant, is more effectively separated from the refrigerant due to its weight and centrifugal force. Therefore, this oil separator is improved in oil recovering efficiency and accomplishes the recent trend of compactness of compressors. However, this internal oil separator is problematic in that lubrication oil or gas refrigerant may leak from the junction between the end cap and the rear housing of the compressor. In addition, the recovered oil return line extends from the oil-storing chamber at a position of a considerable height above the bottom of that chamber and initially and horizontally feeds the recovered oil to the driving part chamber. Therefore, this oil separator may allow gas refrigerant to undesirably flow into the driving part chamber through the oil return line in the case of a low level of recovered oil within the oil-storing chamber. Another disadvantage experienced in the above Korean oil separator resides in that the recovered oil is introduced from the oil-storing chamber into the lower portion within a driving part chamber, thus failing to effectively lubricate the moving parts within the driving part chamber. In addition, when an automobile is moved to the left or right so as to inclinedly position the compressor 120 while running on bumpy road, gas refrigerant may undesirably flow into the driving part chamber.